1. Field of the Invention
This invention relates to a process for manufacturing paint that matches the color of a standard paint. The process involves the steps of (a) addition of the components used in the paint such as a polymeric binder for the paint, solvent for the paint, and colorant in the form of a dispersion or a solution, into a vessel having mixing means; and (b) shading the paint as it is being manufactured. Within the teaching of this invention, the process of shading the paint to match the standard color involves the use of a calculation to determine the theoretical dry color values of the paint being manufactured and to calculate the amount of the components of the paint which must be added to provide a final dry color which falls within the prescribed color tolerance.
2. Description of the Prior Art
Early devices such as those illustrated in Logan et al. U.S. Pat. No. 2,923,438 issued Feb. 2, 1960 provided a method for making paints according to a given formula but did not provide means for color matching the paint to a standard except for visual color matching using estimated additions of colorants to match a standard.
McCarthy U.S. Pat. No. 3,601,589, issued Aug. 24, 1971, and McCarty et al. U.S. Pat. No. 3,916,168, issued Oct. 28, 1975, are directed toward computer controlled methods for preparing paints but use the standard procedure of spraying panels with paint, baking the panels and measuring color value of the panels and calculating and reshading the paint to bring the paint within acceptable color tolerance values.
British Pat. No. 1,589,705, published May 20, 1981, describes a general process for making a paint and adjusting the color values of the paint to come within the color tolerance values of a standard paint. However, this method directly utilizes light scattering and optical absorption properties of colorants used in the paints in combination with reflectance values of the paint at several wavelengths to determine the quantity of colorants required to bring the paint within an acceptable standard.
An article by Ishak in J. Oil Col. Chem. Assoc., 1971, 54, 129-140 teaches the determination of the ratio of dry to wet tristimulus values but fails to teach the use of such a determination as a correction factor for in-process shading of wet paint to match a dry standard.
U.S. Pat. No. 4,403,866 teaches a computer controlled process for matching the color values of a standard liquid paint. This process fails to involve the use of a dry standard color and does not involve the use of correction factors to account for the color change of a wet paint when it dries.
Since the wet paint and a dry sample prepared from the wet paint exist in different areas of color space, utilizing the correction factor as taught herein to shade the wet paint to a theoretical dry color rather than to a wet standard provides a faster, more accurate, shading technique without requiring the production of a number of dry samples during the manufacturing process.